1. Field of the Invention
The invention relates to a method and arrangement for removing gas from a fibre/liquid suspension in a fibre treatment line in a pulp mill, which line includes at least one stage in which the fibre/liquid suspension is treated and/or stored in a large container before being conveyed for further treatment.
2. Description of the Prior Art
It is commonly known that gas bubbles in fibre/liquid suspensions, whether the bubbles occur as free bubbles in the liquid between the fibers or as bubbles bound to the fibers, can lead to problems in different phases of the fibre treatment process. The nature of the problems varies in different parts of the fibre treatment line in the pulp mill, such as interruptions in the flow of the suspension through valves, screens, and so forth, and fibre flocculation, foaming, dewatering problems, and so forth. Also, in a subsequent paper-making machine, the occurrence of gas bubbles in the suspension can cause problems.
The gas in question can, for example, be air, oxygen, and the like. In general it is a question of various gas mixtures
The problem has been addressed in different ways in the prior art. For example, it is known to remove the gas from pumps which transport the suspension between the various treatment stations of the fibre treatment line. However, the capacity of these pumps to remove gas is limited, and this is particularly so when the pump is intended to transport very large flows of fibre/liquid suspension. It is also known to remove gases from large containers in the fibre treatment line, in which containers the fibre/liquid suspension is stored for a long period in order to be stirred and homogenized, for example, or subjected to another treatment. However, the subatmospheric pressure which is needed in such a container in order to achieve the desired degassing requires that the walls of the container be strengthened to such an extent that the overall construction becomes very expensive, which is an obvious disadvantage.